1. Field of the Invention
This invention relates to an apparatus for recording and reproducing packet data on and from a recording medium such as a magnetic recording medium. Also, this invention relates to an apparatus for reproducing packet data from a recording medium such as a magnetic recording medium.
2. Description of the Related Art
A digital satellite system (DSS) and a digital video broadcasting (DVB) system are examples of digital transmission systems. The DSS sends a stream of packets of digital data representing a plurality of programs multiplexed on a time-division basis. Also, the DVB system sends a stream of packets of digital data representing a plurality of programs multiplexed on a time-division basis. The digital data handled by the DVB system is of a predetermined format conforming to MPEG2. Here, MPEG2 is short for "Moving Picture Image Coding Experts Group Phase 2".
In such digital transmission systems, packets sequentially transported from a transmission side represent programs and also identification information pieces for accurate recovery of the programs. In a reception side, the identification information pieces are extracted from a received transport stream of packets, and the programs are recovered from the transport stream of packets in response to the identification information pieces.
There is a known apparatus for recording and reproducing a digital signal on and from a magnetic tape sync-block by sync-block. In this known apparatus, an input digital signal representing a program or programs is divided into sync blocks which are sequentially recorded.
Also, there is a known apparatus for recording and reproducing a transport stream of packets of digital data on and from a magnetic tape. This known apparatus includes a counter outputting a signal representing local reference time which starts from an initial value at start of each recording process or each playback process. During a recording process, the output signal of the local-reference-time counter which occurs at reception of every packet in an input transport stream is added to the packet as a time stamp. Packets including respective time stamps undergo given signal processing before being recorded on the magnetic tape. In this known apparatus, during a playback process, packets reproduced from the magnetic tape are sequentially stored into a buffer memory. The reproduced packets are sequentially read out from the buffer memory. The reproduced packets read out from the buffer memory compose an output transport stream. A time stamp in every reproduced packet is detected. The detected time stamp is compared with the output signal of the local-reference-time counter. When the output signal of the local-reference-time counter comes into agreement with the detected time stamp, reading the related packet from the buffer memory is implemented. This timing control enables the output transport stream to be equal to the input transport stream in packet order and time intervals between packets.